Physics Commons^™

Dynamics Of Disordered Harmonic Lattices, Daniel N. Payton Iii

Doctoral Dissertations

"Extensive numerical and analytic studies of vibrational spectra, normal modes, thermodynamic properties, and dynamical properties of harmonic systems with varying degrees of substitutional disorder have been made. The effects on observable properties of random mixtures of two or more species of atoms with differing masses and differing couplings to nearest-and next-nearest-neighbors have been investigated. Using the IBM-7030 digital computer, spectra for linear chains of 100,000 atoms have been obtained. Calculations in two and three dimensions have been limited to arrays of approximately 1000 atoms. Varying composition, mass ratio, and order affect the spectra in two and three dimensions in ways …

An Investigation Of The Control Of Hydraulic Fracturing Through The Inclusions Of Prefractures, William Joseph Kabeiseman

Doctoral Dissertations

"Among the methods for determining the in-situ state of stress within the earth’s crust, hydraulic fracturing has been and is receiving much attention. This method, in principle, measures stress directly with no delicate electronic equipment required nor knowledge of the elastic modulus of the material.

This dissertation investigates experimentally whether or not control of fracture orientation can be achieved by the introduction of circular and elliptical prefractures along with sand inclusions into cast hydrostone blocks which are hydraulically fractured. A mathematical model is presented and analytically solved for the stress condition associated with a circular crack containing fluid pressure with …

Re-Evaporation Nuclei And Evaporation In A Wilson Cloud Chamber, James G. Smith

Doctoral Dissertations

"Experimental techniques are developed for observing droplet evaporation in the submicroscopic size range. An expansion-compression cloud chamber with an atmosphere of tank helium saturated with water vapor is employed. This work was undertaken with the aim of examining submicroscopic droplet behavior and the existence of re-evaporation nuclei, a form of memory effect.

The theories of evaporation and nucleation on submicroscopic drop residues were re-examined, and alterations which appear to be consistent with the results of this work were incorporated into the evaporation theory.

The observed continually decreasing evaporation rate with diminishing droplet size confirms the existence of re-evaporation nuclei, but …

Calculated Cohesive Energy Of The Ordered Copper-Gold Alloy Cu Au I, Richard W. Hannum

Doctoral Dissertations

"The ordered alloy CuAu is the fifty atomic per cent alloy in the copper-gold system. It was observed by Johansson and Linde(1) and was one of the first ordered alloys to be studied by x-ray diffraction methods(Z, 3). Two ordered superlattices of CuAu are observed. CuAu I exists below 380° C and has a tetragonal structure which is a slight distortion of the face- centered cubic. It is very highly ordered, with all copper and all gold atoms in alternate (002) planes, as shown in Figure 2. CuAu II, which exists between 380° and 415° C, is orthorhombic in structure(4) …

Theory Of The Lunar Photoelectron Atmosphere, Hal Emerson Mccloud Jr.

Doctoral Dissertations

"By considering the mechanics of an electron projected into an arbitrary potential field together with Poisson's equation it is possible to set up a differential equation for the electrostatic potential. The equation may be integrated and the photoelectron density found as a function of height for four approximate models. A simple model based upon monoenergetic photons and monoenergetic electrons ejected vertically upward yields rough estimates of the parameters of interest. Another model takes into account the fact that the photoelectrons are ejected at all angles. A general model takes into account the illumination of the lunar surface by solar (black …

Diffusional Drop Growth In A Supersaturated Atmosphere, John C. Carstens

Doctoral Dissertations

"The effect which a growing droplet has on the supersaturated atmosphere surrounding it is analyzed by assuming a macroscopic diffusional growth mechanism involving both heat and vapor. The problem is solved, for cloud-chamber conditions, first for very short times assuming a fixed radius, and then for longer times assuming the establishment of "quasi" steady-state conditions. Knowledge of the way in which droplet growth affects supersaturation is important in the evaluation of nucleation rates"--Abstract, page ii.